add debugfs.TracepointsWithF

1 files changed, 57 insertions, 0 deletions

diff --git a/internal/debugfs/debugfs.go b/internal/debugfs/debugfs.go
new file mode 100644
index 0000000..80ac436
--- /dev/null
+++ b/internal/debugfs/debugfs.go
@@ -0,0 +1,57 @@
+package debugfs
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Return tracepoints with 'unsigned int fd', which are I/O tracepoints on FDs
+func TracepointsWithFd() ([]string, error) {
+	return tracepointsWith("unsigned int fd")
+}
+
+func tracepointsWith(field string) ([]string, error) {
+	var tracepoints []string
+
+	matches, err := filepath.Glob("/sys/kernel/debug/tracing/events/syscalls/*/format")
+	if err != nil {
+		return tracepoints, err
+	}
+	if len(matches) == 0 {
+		return tracepoints, fmt.Errorf("Unable to gather tracepoints with FDs")
+	}
+
+	for _, formatPath := range matches {
+		has, err := hasField(formatPath, field)
+		if err != nil {
+			return tracepoints, err
+		}
+		if !has {
+			continue
+		}
+		tracepoints = append(tracepoints, filepath.Base(filepath.Dir(formatPath)))
+	}
+
+	return tracepoints, nil
+}
+
+func hasField(formatPath, field string) (bool, error) {
+	file, err := os.Open(formatPath)
+	if err != nil {
+		return false, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.Contains(line, fmt.Sprintf("field:%s;", field)) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}